Humans are the only primates that have a white sclera that contrasts with the darker colored iris (Kobayashi & Kohshima, 1997). While color and darkness of skin, hair, and iris vary widely among humans, the color of sclera is universally white and lighter than the iris. Hence, all human faces share a common contrast polarity relationship between the sclera and iris, in addition to the first order spatial relationships between the facial features (two eyes above a nose, which is above a mouth). Here, we test the possibility that the contrast polarity relationship between the sclera and iris plays an important roll in facial processing by infants.

Forty-eight 7–8 month-old-infants participated in the present study. We employed a familiarization/novelty preference procedure to test face discrimination in infants. During familiarization phase, infants were repeatedly shown a female face for six 15 sec trials. Then, they were shown the familiarized female face and a novel female face side by side for two 10 sec trials. Infants showed a significant looking preference for novel face only in the Positive Face and Positive Eyes conditions. These results show that infants only discriminate between the faces when the contrast polarity of the eyes is preserved, irrespective to the contrast polarity of facial surface and is consistent with a critical role for the contrast polarity of eyes in infants' face perception. We will present further data from adult participants.

This research was supported by PRESTO, Japan Science and Technology Agency and a Grant-in-Aid for Scientific Research (18300090, 20119002) from Japan Society for the Promotion of Science(JSPS), and by a Grant-in-Aid for JSPS Fellows (196068).